1962 was the year a coal mine started in Centralia, PA that could po­ten­tial­ly burn for some time yet to come. The fire caused most people in the town to evacuate by the mid-1990s leaving a few who decided to stay. It is literally a slow, smoldering, un­der­ground hazard. According to the linked article there are a number of ongoing un­der­ground and surface coal fires in the US.

Marsh­mal­lows anyone?